docs: def emit_func(self, cuin, *args, **kwargs):
          """Emit a cuin(with dfp) and gets the func result.
  
          :param cuin: str,unicode: Callback Unique Identifier Name.
  
          :param args: list: Variable length parameter for cuin.
  
          :param kwargs: dict: Keyword parameter for cuin.
  
          :returns: The result of calling the function.
  
          .. versionadded:: 2.3.0
          """
          if cuin and isinstance(cuin, string_types):
              if cuin in self._dfp_funcs:
                  f = self._dfp_funcs[cuin]
                  return f(*args, **kwargs)
              else:
                  raise DFPError("The cuin does not exist")
          else:
              raise DFPError("Invalid parameter")